This invention relates generally to geophones, and more particularly to a high-sensitivity geophone with an improved signal-to-noise ratio.
A geophone is an instrument used to transform seismic energy or vibrations into a voltage signal. A conventional geophone includes a single coil and a ferromagnetic mass (e.g., a magnet), both of which may be contained in a housing. Springs may support the coil, thus allowing motion in one dimension relative to the housing. The magnet may be fixed with respect to the housing and, as the geophone is vibrated, the coil may move relative to the magnet. The relative motion of the coil may induce an electromotive force, or voltage, in the coil. A “single-coil” may include a single, continuous length of wire has been wound into a coil, and that connection to the coil is available at the two ends, or terminals, of the wire. The voltage across these two terminals may provide the output signal from the device. This voltage may be proportional to the velocity of the housing for frequencies above the natural resonant frequency of the spring-coil-mass system.
One of the drawbacks encountered with the above-referenced design is the inability to increase the sensitivity of the geophone without dramatically increasing the size of the geophone (e.g., the length of the coil and/or the size of the ferromagnetic masses). Increasing the size of the geophone generally leads to decreased portability and increased operating costs. Therefore, it would be desirable to provide a more sensitive geophone with a higher signal-to-noise ratio.